I think I've sent everyone on a wild Goose chase (sorry).

Mackrackit's Tx code was working fine all along.

I now think It's the Rx program that holds the key. The reason I think this is becasue Bruce's Rx program (as I understand it) looks to reset if no data recieved within 65ms of button press ( that's why the data only ever Tx'd with a button actually pressed). Any timing loop throws out the 65ms data arrival, hence no flahing led.

I commented out a section of the Rx program and although not working perfectly, the Rx led now flashes after the time delay and data is sent.

What do we think? Am I on to something here?

Again apologies for the curved ball.

Dave